Field of the Invention
The present invention relates to a control apparatus for an automatic transmission.
Description of the Related Art
An automatic transmission generally includes planetary gear mechanisms and engaging mechanisms such as a clutch and a brake, and implements each gear range by switching the power transmission path by the engaging mechanisms. As the engaging mechanisms, employing a mechanical engaging mechanism has been proposed in addition to a hydraulic engaging mechanism. In particular, an arrangement that uses a clutch (two-way clutch) capable of switching to a state to do two-way rotation restriction as a brake has been proposed (for example, Japanese Patent Laid-Open No. 2014-202340).
When the two-way clutch is used as a brake, a rotational element connected to the two-way clutch can be switched between a state in which rotation is restricted only in one direction (rotation in the reverse direction is permitted) and a state in which rotation is restricted in both directions. When switched to the state in which rotation is restricted in both directions, the rotational element connected to the two-way clutch is fixed to the casing. For this reason, if switching is done during rotation of the rotational element, unusual noise or vibration occurs, and the two-way clutch breaks. To prevent this, switching may be performed via an engaging combination that brings the rotational element to a standstill.
In an arrangement that switches the two-way clutch to the state in which rotation is restricted in both directions when switching the gear range from the forward range to the reverse range, processing of switching the state of the two-way clutch is needed before the reverse range is put in gear. During this processing, if the driving transmission between the input shaft and the output member of the automatic transmission is disconnected, and the driving wheels are freely rotatable, the sense of response to the shift operation to the reverse range may be weak.